Security was held to be an area of the Brexit negotiations where the United Kingdom could negotiate an outcome embodying both continuity and generous terms owing to the indivisibility of strategic interests, the low salience of security cooperation, and the intergovernmental nature of cooperation. Yet considerable divergence in outcomes emerged between internal and external security matters: In external security, expectations of a comprehensive agreement were dashed, with both sides resorting to an entirely unstructured relationship (Martill and Sus, 2021). In internal security, considerable continuity in cooperation between police and judicial authorities was maintained with arrangements going beyond practitioner’s expectations (Davies and Carrapico, forthcoming 2025). This variation is puzzling, not least given the commonalities of security cooperation, but also the higher sovereignty costs involved in internal security matters. In this article, we argue that the variation can be explained by the degree of symmetric interdependence in the internal security domain, the absence of feasible alternative venues to cooperate with EU member states in this area as well as the increasing politicisation of external security matters and the resulting incentives on both sides to demonstrate greater autonomy in this area. Wishing to contribute to the existing literature on UK foreign policy and its approach to Brexit negotiations (Glencross, 2022; Meislova and Glencross, 2023), our argument helps explain the conditions under which continuity can be negotiated following exit from an international organisation and highlights distinct domain-specific dynamics within UK-EU security cooperation which have received little attention to-date.

Russia’s full-scale invasion of Ukraine has significantly tested the resilience of NATO and the EU, driving unprecedented levels of military and non-military assistance. This paper examines how member states of these organizations, notably those in Europe, have responded to this geopolitical disruption, with a particular focus on the spatial dynamics of aid provision. Using spatial econometric analysis, we explore whether countries under intense geopolitical pressure exhibit free-riding or following behaviors.

The study leverages fine-grained data from the Ukraine Support Tracker (UST) by the Kiel Institute, which offers monthly data—a departure from the standard periodicity typically employed in analyses of military spending or other aggregate state-level expenditures like foreign aid. The use of monthly data suggests that interdependencies among Ukraine’s key partners evolve rapidly, with national governments swiftly considering and responding to their peers’ allocation decisions. This high frequency, however, may fail in detecting spatial dynamics if the pace of decision-making is slower. To address this, we complement our analysis with quarterly data to ensure robustness.

Overall, our findings reveal that heightened geopolitical threats can disrupt traditional spending habits, challenging established theories of free riding by smaller NATO countries, in particular. These shifts tend to point to the alliance’s ability, at least in the short term, to maintain effective collective action, even as burden-sharing remains uneven more generally. By uncovering positive spatial interdependencies, the paper highlights following behavior as a potential mechanism for reinforcing resilience in collective action strategies, particularly in response to geopolitical crises.

Regional organisations have never lacked sky-high ambition. NATO’s unrealised 2% defence expenditure goal might be extended to 5% under President Trump; the EU abolished its aim of being a normative power in favour of pursuing the ‘strategic autonomy’ of a European Defence Union; and the African Union’s objective to self-finance its peace operations and ‘silence the guns by 2030’ remains far out of reach. Against the backdrop of contested multilateralism and a track record of failures of past over-ambitious reforms, the literature expects no reforms or gradualist reforms reflecting a minimal lowest common denominator. Yet international organisations (IOs) persist in seeking overly ambitious reforms. And despite obvious shortcomings, all these policy proposals possess productive power for the organisations and their members in advancing regional integration and cooperation. To make sense of this puzzle, this article asks: Why do states willingly engage in unrealistic institutional reforms and policy goals of a regional integration process? The article theorises the role of overpromised and underdelivered reforms in regional integration, introducing ‘aspirational reform’ as a distinct mechanism that enables IOs to secure paradoxical ex-ante commitments to demonstrably unrealistic policy goals. The main argument asserts that states deliberately engage in aspirational reform in a regional integration process when system- and unit-level incentives align. Namely, states’ use of aspirational reforms depends on the unit-level scope conditions of timeliness, the substance of proposed reforms, and the IO’s bureaucratic credibility at delivering at least partial results. At the unit level, states need to perceive domestic benefits from engaging in aspiration reforms, including status-seeking and access to public goods generated by aspirational reform. Drawing from prospect theory, organisational theory, and regionalism studies, the article offers a generalisable theory of how actors desigb IO reforms that link discursive promises of long-term objectives with only partial short-term implementation. Through a Global IR lens and case studies of security policies at NATO, the EU, and the African Union, this analysis contributes to the study of regional integration and alliance theory, offering an explanation for the longevity of IOs facing growing obstacles for effective integration.